Some devices, such as electronic readers use electrophoretic displays (EPDs). The devices that use EPDs are sometimes referred to as electronic paper (e-paper) or electronic ink. EPDs may have very high resolution that may be comparable with liquid crystal displays. One of the unique properties of EPDs is that they reflect light rather than emit light; therefore, they simulate paper in that light reflects from the EPD. The EPDs are static in that individual pixels are turned dark or bright depending on the material being displaced to the display visible surface. For that reason, once a pixel is set, it will stay in that state indefinitely, even after power has been removed. Therefore, EPDs can display images for a long period using minimal or no power.
There are two formats for driving EPDs. A first format is wherein each pixel is controlled independently, which is sometimes referred to as the pixelar format. The pixelar format also allows for an EPD to change images very fast. However, the pixelar format requires a very high bandwidth and memory consumption to operate and may not be necessary for most applications.
The second format for driving EPDs is sometimes referred to as the regional format. In the regional format, groups of pixels are controlled or changed simultaneously. For example, the regional format may display a plurality of non-overlapping rectangles. A plurality of rectangles may form text that is displayed on the EPD. The regional format uses much less bandwidth and memory than the pixelar format because a lot of data stored to hold the display context is the same for all pixels. This format may provide high resolution, but it does not enable quick changes to images displayed on an EPD.